Attractive Forces Between Global Monopoles and Domain Walls

We study the interaction between stable monopoles and domain walls in a $SO(3) \times Z(2)$ scalar field theory. Numerical simulations reveal that there is an attractive force between the monopole and the wall, but that after the monopole and the wall collide, the monopole does not unwind. We present an analytic explanation for the origin of the attractive force, and conclude that this is a generic feature of monopole-wall interactions which does not depend on the detailed structure of the model. The existence of the attractive force supports the hypothesis of Dvali {\em et al.} (hep-ph/9710301), who proposed that monopoles can be ``swept up'' by domain walls, thereby alleviating or solving the monopole problem associated with phase transitions occurring after or in the absence of inflation.